Dental pulp tester

ABSTRACT

A compact battery operated dental nerve stimulator, commonly referred to as a pulp tester is constructed so that a patient is not required to hold a ground electrode and so that the output voltage stimulus can be varied with one hand while the probe electrode remains in contact with the patient&#39;&#39;s tooth. A logarithmic output level control permits the operator to very gradually change the stimulus level at low voltages in order to minimize patient discomfort in situations where a tooth may be hypersensitive and to rapidly change stimulus level at higher voltages for the purpose of testing teeth with reduced sensitivity. Additionally, a switch is provided for turning the stimulus on and off independent of outout level and to simultaneously illuminate the work area.

United States Patent [191 Friedman Septd, 1973 DENTAL PULP TESTER Joshua Friedman, 350 E. 30th St., New York, NY. 10016 22 Filed: Mar. 3, 1972 21 Appl. No.: 231,491

[76] Inventor:

[56] References Cited UNITED STATES PATENTS 3,207,151 9/1965 Takagi 128/21 R Primary Examiner-Robert Peshock Attorney-Bernard Ouziel [57] ABSTRACT A compact battery operated dental nerve stimulator, commonly referred to as a pulp tester is constructed so that a patient is not required to hold a ground electrode and so that the output voltage stimulus can be varied with one hand while the probe electrode remains in contact with the patients tooth. A logarithmic output level control permits the operator to very gradually change the stimulus level at low voltages in order to minimize patient discomfort in situations where a tooth may be hypersensitive and to rapidly change stimulus level at higher voltages for the purpose of testing teeth with reduced sensitivity. Additionally, a switch is provided for turning the stimulus on and off independent of outout level and to simultaneously illuminate the work area.

6 Claims, 5 Drawing Figures Patented Sept. 4, 1973 3,755,900

2 Sheets-Sheet i Fig. 2

Patented Sept. 4, 1973 3,755,900

2 Sheets-Sheet :i

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DENTAL PULP TESTER My invention relates to an apparatus for determining the vitality of teeth commonly referred to as a dental pulp tester and, more particularly, to a compact, battery powered unit that can easily be operated and adjusted with one hand in a fashion that minimizes the possibility of patient discomfort.

When a tooth has been subject to decay, physical trauma, thermal changes or irritation by sweet foods or deep fillings, the pulp tissue becomes inflamed. When this inflammation is left untreated for a long time, the ensuring pulpal inflammation generally proceeds to a severe infection with abscess formation about the root tips. It is at this stage that many teeth require extraction and that endodontic procedures, designed to hel remove this infection, are least successful.

Electric devices used to test the vitality of pulpal tissue have long been used as diagnostic aids by dentists. For example, these devices have found application where a patient complains of pain on one side of the mouth and cannot isolate the specific tooth from which the pain emanates. Also they have been used in the diagnosis of decay which developes around the borders of fillings in teeth with existing restorations a situation where X-rays alone may not indicate the presence or extent of the decay.

in actual operation, a stimulating electrode of an electric pulp tester is applied to a dried tooth which is undergoing examination. The operator then gradually raises the level of the voltage at the electrode until the patient feels a tingling or mild electric shock in the tooth that is being touched by the electrode. By comparing the voltage level to which the patient responds with the level at which other of his normal teeth respond, the dentist can make a diagnosis on the state of inflammation or vitality of the dental pulp in the tooth under examination.

While the existing dental pulp testers have proved to be valuable diagnostic tools, they suffer from certain disadvantages which have limited their utility. For example, many existing pulp testers are powered from line voltage and current and require the patient to hold a common or ground electrode in order to complete the stimulating circuit. The use of line power limits portability and creates an obvious shock hazard both to the dentist and to the patient. The requirement that the patient hold a ground electrode has a negative psychological effect on the patient, increasing his fear of the test procedure.

Over the years, improvements have been made to dental pulp testers so that now there are units which are battery operated and which also utilizes high frequency stimulus pulses as a means for eliminating the need for ground electrodes. However, these units still contain certain inherent deficiencies which limit their utility. Illustratively these units are designed so that they are activated by an ON-OFF switch which is also part of the control potentiometer used to vary stimulus voltage. The voltage is directly proportional to the angular position of the control potentiometer with no means to turn the output stimulus on and off independent of the output level. Furthermore, the controls on such units are positioned so that it is difficult, if not impossible, to adjust the stimulus level with one hand while the device is in the oral cavity. As a consequence of these factors, existing battery operated devices still present a shock hazard because an energized or hot stimulating electrode that had been adjusted to test the sensitivity of a dead nerve (i.e., adjusted for a very high output voltage stimulus) may cause the patient to suffer an uncomfortable shock when the probe is inadvertently brushed against his lips, cheek or adjacent teeth during the diagnostic procedure. Thus, each time the probe must be removed from his mouth for an adjustment of the stimulus voltage, the patient is either exposed to a shock hazard or the dentist must repeatedly switch the unit off and readjust the output level with the consequent delay and annoyance to both the dentist and the patient.

Accordingly, it is an object of my invention to provide a compact reliable battery operated portable dental pulp tester which is completely self-contained unit, requiring no electrical connection to any other auxiliary apparatus.

It is still another object of my invention to provide a dental pulp tester in which a solid-state oscillator is activated by a conveniently placed push button ON-OFF switch and a separate conveniently placed calibrated dial is provided to control the output stimulus voltage so that the change is very gradual at low numbered dial settings and more abrupt at higher dial settings.

It is an additional object of my invention to provide a dental pulp tester having a lamp which simultaneously serves to illuminate the oral cavity and as a means for determining whether the battery level is adequate and the unit is operational.

In accordance with the foregoing and other objects and features of the invention, l have provided a lightweight, compact, portable dental pulp tester having a probe electrode connected to the output of a battery powered transistorized oscillator circuit. The oscillator output voltage is derived from the slider of a logarithmic potentiometer selected so that the voltage variation is very gradual over a first portion of its range and very rapid over a second portion of its range. The battery and oscillator circuit are contained within a metal or electrically conductive plastic cylindrical housing fitted with an opaque optically conductive plastic nose piece hollowed to receive a lamp which simultaneously illuminates the oral cavity and produces an indication that power has been applied to the oscillator. The nose piece also encloses a friction chuck mechanism designed to accept a replaceable insulated electrode probe. Additionally, a calibrated dial, mechanically connected to the potentiometer slide, is positioned so that its plane of rotation is parallel to and through the longitudinal axis with a segment extending through the housing to permit easy fingertip control of the oscillator output voltage, and an ON-OFF normally open single pole single throw push button switch is mounted with the push button extending through the wall of the housing contiguous to the dial. This switch energized both the oscillator and the lamp without affecting the dial setting.

These and other objects and features of my invention will be better understood if reference is had to the following detailed description and accompanying drawing in which:

FIG. 1 is a perspective view of the apparatus;

FIG. 2 is a sectional view taken through the longitudinal axis of the apparatus shown in FIG. 1;

FIG. 3 is a schematic circuit showing the pulse oscillator circuit used to energize the electrode probe;

FIG. 4 shows the output voltage waveform derived from the oscillator shown in FIG. 3; and

FIG. shows the logarithmic characteristics of the potentiometer connected to the output of the oscillator;

Referring now to the drawing, FIGS. 1 and 2 show the general construction and arrangement of parts in the dental pulp tester. A hollow cylindrical tubing forms a housing 1 to which are fastened a control panel 2, a nose piece 3 and an end cap 4 and in which is mounted a circuit board 5 containing the electrical circuit components. Housing 1 is preferably constructed from an electrically conductive material, but may be fabricated from non metalic materials so long as a portion of the outer surface normally in contact with the dentist's hand is connected to the circuit ground. For ease of manipulation it is generally preferable to limit the housing length to six inches. Nose piece 3 is conical in shape, containing a friction chuck 6 positioned within a concentric hole bored through nose piece 3 and a lamp 7 positioned within a partially bored eccentric hole. Nose piece 3 is fabricated from an opaque optically conductive plastic and lamp 7 is a subminiature incandescent bulb commonly known as a grain of wheat lamp. Lamp 7 is preferably selected to have an operating voltage somewhat above the voltage of the battery 8 in order to obtain a useful life in excess of 100,000 hours. In the arrangement shown lamp 7 provides illumination that is visible over a wide viewing angle, by means of internal reflection within the nose piece. ensuing help Also part of the apparatus is a spring 11 and a probe 9 constructed from a metalic electrode enclosed within an insulated sleeve. Probe 9 extends axially from chuck 6 and terminates in a tip bent at an acute angle away from the axis. Protruding from the tip is a metalic or conductive elastomer contact surface which may be spherical in shape. A short length of the other end of probe 9 is stripped of insulation in order to facilitate a positive electrical contact with the jaws of chuck 6 in which it is fixed and held by friction. Optimally, probe 9 will extend 1 to 2% inches from the end of chuck 6.

Spring 11 serves as both an electrical connection from one terminal of battery 8 to cap 4 and housing 1, as well as a means for properly positioning battery 8 so that its other terminal makes electrical contact with circuit board 5 at terminal 12. Cap 4 is provided with a coin slot as a means for facilitating its removal to replace battery 8. The means by which these components are assembled include screw 13 to fasten control panel 12 to nose piece 3, screw 14 to fasten nose piece 3 to housing 1, screw 15 to fasten control panel 2 to circuit board 5, screw 16 to fasten circuit board 5 to housing 1 and make electrical contact therewith and screw 10 to hold chuck 6 so that it makes electrical contact with circuit board 5.

Circuit board 5 contains transistor 17, capacitor 18, resistors 20 and 21, switch 22, transformer 23 and potentiometer 24, all of which when connected to battery 8 form the blocking oscillator circuit depicted in FIG. 3. While FIG. 3 describes a particular blocking oscillator circuit, those versed in the art will recognize that other pulse type circuits may be used with equal facility.

In the case of the circuit shown, the oscillator is energized when the spring loaded normally open single pole switch 22 is closed, causing battery 8 to supply current through resistor 21 and forward bias th emitter base junction of transistor 17. This causes transistor 17 to being to conduct and a voltage to build up across that portion of the primary winding of step up transformer 23 in the collector circuit of transistor 17. This in turn induces a voltage across the other portion of the primary winding of transformer 23 with polarity such that current flowing therefrom increases the forward bias of the emitter base junction of transistor 17. This additional bias current very rapidly drives transistor 17 into saturation while simultaneously charging capacitor 18 with the polarity shown. After a while capacitor 18 becomes sufficiently charged to back bias the base emitter junction of transistor 17 and cause transistor 17 to cut off. When this occurs, capacitor 18 begins to discharge through resistors 20 and 21 until a point where the emitter base junction of transistor 17 begins to conduct once again, and repeat the cycle.

The output voltage wave form across the secondary of transformer 23 is shown as a function of time in FIG. 4. By properly selecting the values of capacitor 18 and resistors 20 and 21, one can control the period of oscillation. Experience has shown that the optimum frequency of operation is in the range of between 400 and 4,000 cycles per second. As will be understood by those versed in the art, the turns ratio of transformer 23 can be selected so that the oscillator will operate from a battery on the order of 4 volts and produce a peak to peak output voltage on the order of 400 volts which has been found to be sufficient for diagnostic purposes.

The ends of potentiometer 24 are connected across the secondary of transformer 23 and the slide terminal is connected to probe 9. The resistance taper of potentiometer 24 is logarithmic and is shown as a function of dial setting in FIG. 5. As the slider is moved away from the terminal connected to ground, the voltage increases very slowly until the approximate physical midpoint of potentiometer 24. Then, as the slide moves from the midpoint to the other end of potentiometer 24, the voltage increases very rapidly. The voltage applied to the tip of probe 9 drives a current through the patients tooth and body, through the dentist who makes electrical contact with the patient and back to ground through housing 1.

As shown in FIGS. 1 and 2 a wheel-like calibrated dial 24 is mounted on circuit board 5 so that its circular cross section is in a plane parallel to and running through the longitudinal axis of housing 1 with a seg ment protruding perpendicularly through control panel 2. Dial 24 is affixed to circuit board 5 so that it may be easily rotated with an index finger while the dentist places the pulp tester probe on a patients tooth. Dial 24 is mechanically ganged to the slider of potentiometer 24 and so controls the magnitude of the oscillator output voltage appearing at the tip of probe 9 connected through screw 10 and chuck 6. The circumferential edge of dial 24 is calibrated with evenly distributed spaced graduations which may be numbered 0 through 10.

A separate push button switch 22 is mounted on circuit board 5 perpendicular to the longitudinal axis between dial 24 and nose piece 3 so that the button protrudes perpendicularly through panel board 2. As shown in FIG. 3, switch 22 is of the single pole single throw type designed so that it is closed when the button is depressed by the dentists finger. When this occurs it connects the negative terminal of battery 8 to the center tap of the primary of step up transformer 23 to energize the oscillator and produce an output voltage at probe 9. It simultaneously completes the circuit to illuminate lamp 7 which is connected directly across battery 8. In this fashion lamp 7 serves both to illuminate the oral cavity and as an indicator to provide information that power has been applied to the oscillator circuit and battery level is adequate.

As a result of the relative positions of switch 22 and dial 24 the dentist may, with one finger, alternately vary the stimulus voltage by rotating dial 2d and momentarily apply it to the tooth surface by depressing the button of switch 22 without removing probe 9 from the oral cavity and tooth surface, or removing his eyes from the tooth in question.

By this arrangement the dentist, if he wishes, may safely remove the probe from the oral cavity without the dangerof electrical shock and exactly duplicate the level of the prior stimulus (if the dial is not moved) when the probe is later reinserted. He can also maneuver his index finger between dial 24l and switch 22 while the probe is in the oral cavity and in contact with the tooth to incrementally adjust the probe voltage in accordance with the characteristic shown in FIG. 5.

It is to be understood that the above-described arrangements are illustrative of the application of the principles of the invention. Numerous other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

l. A dental pulp tester comprising an elongated housing; a probe extending from said housing; means contained within said housing for generating stimulus voltage between said housing and said probe for application to a test area including an oscillator circuit having a potentiometer to control the magnitude of said voltage, a battery and a normally open ()N-OFF switch connecting said battery to said oscillator circuit; button means for actuating said ON-OFF switch disposed outside and perpendicular to the longitudinal axis of said housing; and a circular dial ganged to said potentiometer disposed in a plane parallel to and running through the longitudinal axis of said housing with a segment protruding perpendicularly from said housing contiguous to said button means.

2. A dental pulp tester in accordance with claim ll wherein said potentiometer has .a logarithmic resistance taper which gradually increase between one end and the physical midpoint of said potentiometer and which increases rapidly between the midpoint and the other end of said potentiometer.

3. A dental pulp tester in accordance with claim 2 further comprising an optically conductive nose piece disposed between said housing and said probe, a lamp, and a friction chuck disposed within a through bored hole in said nose piece adjusted to accept and make electrical contact with said probe, and wherein said lamp is disposed within a partially lbored eccentric hole in said nose piece.

4. A dental pulp tester in accordance with claim 3 wherein said ON-OFF switch is connected to simultaneously energize said oscillator and said lamp independently of said potentiometer.

5. A dental pulp tester in accordance with claim 4 wherein said housing is a hollow electrically conductive cylinder, a panel board is fastened on the wall of and parallel to the longitudinal axis of said housing at a first end thereof contiguous to said nose piece, a cap is screwed to a second end of said housing and wherein said button means is disposed between said nose piece and said dial through said panel.

6. A dental pulp tester in accordance with claim 5 wherein said oscillator circuit consists of a single transistor blocking oscillator mounted on a circuit board fastened to said housing and connected to produce output voltage pulses having peak to peak magnitude in the range between 300 and 400 volts and afrequency in the range between 400 and 4,000 cycles per second. F =8 i= 

1. A dental pulp tester comprising an elongated housing; a probe extending from said housing; means contained within said housing for generating stimulus voltage between said housing and said probe for application to a test area including an oscillator circuit having a potentiometer to control the magnitude of said voltage, a battery and a normally open ON-OFF switch connecting said battery to said oscillator circuit; button means for actuating said ON-OFF switch disposed outside and perpendicular to the longitudinal axis of said housing; and a circular dial ganged to said potentiometer disposed in a plane parallel to and running through the longitudinal axis of said housing with a segment protruding perpendicularly from said housing contiguous to said button means.
 2. A dental pulp tester in accordance with claim 1 wherein said potentiometer has a logarithmic resistance taper which gradually increase between one end and the physical midpoint of said potentiometer and which increases rapidly between the midpoint and the other end of said potentiometer.
 3. A dental pulp tester in accordance with claim 2 further comprising an optically conductive nose piece disposed between said housing and said probe, a lamp, and a friction chuck disposed within a through bored hole in said nose piece adjusted to accept and make electrical contact with said probe, and wherein said lamp is disposed within a partially bored eccentric hole in said nose piece.
 4. A dental pulp tester in accordance with claim 3 wherein said ON-OFF switch is connected to simultaneously energize said oscillator and said lamp independently of said potentiometer.
 5. A dental pulp tester in accordance with claim 4 wherein said housing is a hollow electrically conductive cylinder, a panel board is fastened on the wall of and parallel to the longitudinal axis of said housing at a first end thereof contiguous to said nose piece, a cap is screwed to a second end of said housing and wherein said button means is disposed between said nose piece and said dial through said panel.
 6. A dental pulp tester in accordance with claim 5 wherein said oscillator circuit consists of a single transistor blocking oscillator mounted on a circuit board fastened to said housing and connected to produce output voltage pulses having peak to peak magnitude in the range between 300 and 400 volts and a frequency in the range between 400 and 4,000 cycles per second. 